1. Technical Field
The present invention relates to display devices, and more particularly to thin film transistors having a crystalline channel that meets low-temperature processing requirements of low-cost and/or flexible substrates.
2. Description of the Related Art
Mainstream thin film transistor (TFT) devices are comprised of amorphous or polycrystalline materials as active channel materials. One reason for the use of such materials is that amorphous and polycrystalline materials permit large area and low cost deposition. This is particularly suitable for low-cost substrates such as glass or flexible plastic. However, the performance of these devices (particularly mobility and therefore drive current and switching speed) is limited by the non-crystalline nature of the semiconductor active material. On the other hand, high processing temperatures typically required for crystalline semiconductor materials are not compatible with low-cost substrates associated with amorphous and polycrystalline devices.
Active matrix TFT organic light emitting diode (OLED) displays employ amorphous and polycrystalline devices. Typically amorphous hydrogenated silicon (a-Si:H) or low temperature polysilicon (LTPS) TFTs are employed as a backplane. However, the mobility of a-Si:H is too low for high resolution OLED displays, and LTPS suffers from device-to-device threshold voltage (VT) variation and compensation circuitry limit resolution.